Two Tools for Prototyping Legal CBR

When representing a body of case law it is invaluable to have a means of executing the representation to check and refine the representation. This is better done using generic tools, since the focus can then be on the representation itself, rather that on the software using it. In this paper we prototype a novel representation of cases as dimensions [1], using a standard spreadsheet (Excel) which gives a numeric analysis and the web service Carneades [3], which allows visualisation of the representation. The domain modelled was that of the famous wild animals property law cases together with Popov v Hayashi, introduced in [4]. Fuller details can be found in [2]. An analysis of the cases in terms of dimensions was offered in [1], to accommodate different degrees of presence of factors. The idea here is that factors represent sub-ranges of dimensions. As we move from extreme pro-plaintiff to extreme pro-defendant the plaintiff is less and less favoured by the dimension. At some point the defendant will start to be favoured. As we approach issues, we may need to introduce thresholds, so that a binary decision, required in a legal case, can be made. Three thresholds are required for our cases: to determine how close the pursuit needs to be to give possession to the plaintiff; to determine whether the land belongs to the plaintiff in a way which gives possession of the animals; and a threshold for where the law should intervene. The thresholds are represented by setting appropriate flags. Spreadsheet Implementation. The spreadsheet has four areas: a data area to hold the case vectors, a flags area for the thresholds, an abstract factors area, used to propagate the initial values, and an issues area to resolve the issues. The heart of the model is in the abstract factors area. Here each cell represents one or two arguments, justifying the content of the cell. This can be realised using an IF...THEN...ELSE formula. Finally we reach the issue area, which indicates the degree to which each party is favoured on that issue. It is up to the user to decide whether the plaintiff is sufficiently favoured. The spreadsheet provides a systematic way to rapidly prototype an implementation of a dimensional analysis. As such it makes an excellent environment for the exploration of the effects of different flags and refinement of the rule set. The spread sheet is downloadable from The …